[R] first occurrence of a value?

[Dimitris Rizopoulos]

another approach is:

df <- data.frame(j1999 = c(0,0,0,0,1,0), j2000 = c(NA,1,1,1,0,0),
     j2001 = c(1,0,1,0,0,0))

years <- as.numeric(gsub("^[^0-9]+", "", names(df)))
ind <- apply(sapply(df, "==", 1), 1, function (x) which(x)[1])
df$year <- years[ind]


I hope it helps.

Best,
Dimitris


On 5/4/2011 1:52 PM, Albert-Jan Roskam wrote:
> Hello,
>
> A simple question perhaps, but how do I, within each row, find the first
> occurence of the number 1 in the df below? I want to use this position to
> programmatically create the variable 'year'. I'v come up with a solution, but I
> find it downright ugly. Is there a simpler way? I was hoping for a useful
> built-in function that I don;t yet know about.
>
> df<- data.frame(j1999=c(0,0,0,0,1,0), j2000=c(NA, 1, 1, 1, 0, 0), j2001=c(1, 0,
> 1, 0, 0, 0), year=c(2001, 2000, 2000, 2000, 1999, NA))
> library(gsubfn)
> x<- apply(df==1, 1, which)
> giveYear<- function(df) { return( as.numeric(gsubfn("^[^0-9]+", "",
> names(df)[1])) ) }
> df$year2<- sapply(x, giveYear)
>
> Thanks in advance!
>
>   Cheers!!
> Albert-Jan
>
>
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-- 
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus University Medical Center

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